4 


Properly  cf  «&  L'r.ilid  ;       Covernmer. 


i 


I  aited  States  k-prinmnn  Si  .\"ju 

\U     OP      KNTOMOLO 

:   and  Chic!  ol   i)«**ui 


I  III     (  URN    LEA  I    \  PHIS    VM»    (  dI:n    ROO 

Bj   I     M    '■' 

Tli>»  coin  leaf  -aphis  (^  dis  Fitch)  and  the  corn  root-aphis 

(Aphis  orbcs)  are  together  made  the  subjects  of  tlii- 

circular  because  l>otli  attack  growing  corn,  because  it  has  yel  to  !».■ 
clearly  shown  thai  there  is  no  direct  kindred  connection  between 
them,  though  it  is  possible  that  they  are  distinct  s]  ind  because 

thi>  question  of  their  identity  or  relationship  presents  itself  to  almost 
every  ol»ser\  ing  farmer. 

The  leaf-aphis  does  the  farmer  little  direct  injury.  The  root-aphis, 
on  the  other  band,  sucks  the  sap  from  the  roots  of  his  corn',  then 
causing  the  plants  t"  become  dwarfed,  and  in  serious  cases  the  leaves 
turn  brown  and  die.  In  an  infested  field  the  corn  will  !»<■  "spotted,'1 
as  farmers  term  it  thai  is,  while  "the  plants  on  certain  areas  in  the 
field  may  make  a  normal  growth  and  mu\  ear  well  later  on,  those 
on  other  areas  will  make  little  growth,  but  tassel  out  after  they  have 
become  n  foot  or  a  foot  and  ;i  half  high,  producing  the  almost  worth- 
less ears  known  as  "i  or  none  ;it  all.  Thus  the  dun 
the  crop  in  Bome  fields  at  times  reaches  50  per  rent  or  more,  and  the 
annual  loss  throughout  the  corn  belt  must  amount  to  well  on  toward 
a  million  dollars.  This  root-aphis  is  really  becoming  the  most  serious 
the  many  insect  peats  ot  the  cornfield,  especiallj  where  a  atricl 
system  of  crop  rotation  is  not  carried  out. 

THE    CORN    LEAF-APHIS 

The  corn  leaf-aphis  (figs.  1,2)  was  descril»ed  by  l>r.  Asa  Fitch  in 
L856  from  eastern  New  York,  but  it  is  now  known  to  occur  from  New 
England  to  North  Dakota  and  Texas,  as  well  as  on  the  Pa<  ific  coast. 
Besides,  it  was  found  by  the  writer  in  great  abundance  '»\  sorghum 
on  the  grounds  of  the  Agricultural  College  of  South  Australia,  at 
Roseworthy,  February  '•'.  1889.     !'  L  »wrie,  at  that  time  prin- 

cipal of  the  college,  assured  the  writer  that  it  sometimes  becam 
essivelj  abundant  as  to  render  the  plants  obnoxious  as  foddei   for 


stock.  The  insect  is  known  also  from  Japan.  In  our  own  country, 
while  not  usually  a  serious  pest,  it  is  said  to  damage  corn,  sorghum, 
and  barley  in  Texas,  while  Doctor  Forbes  has  noted  a  reddish  dis- 
coloration due.  he  thinks,  toa  bacterial  effect  following  its  occurrence 
on  broom  corn. 

APPEARANCE    AM)    HABITS. 

The  corn  leaf-aphis  is  bluish  green  in  color.  It  appears  on  corn 
throughout  the  Middle  West  early  in  July — about  the  time  that  the 
root-aphis  begins  to  decrease  in  numbers  on  the  roots — sometimes 
literally  swarming  on  the  leaves,  husks,  and  tassels.  Here  it  gives 
birth  to  its  young,  and  disappears  from  the  plants  only  as  these  ripen 
and  become  dry,  some  individuals  even  remaining  among  the  husks  of 
belated  ears  until  freezing  weather  kills  them  outright. 

AYhence  these  insects  come,  in  July,  when  the  first  few  winged 
females  appear  on  the  leaves  of  the  corn,  is  a  mystery,  equaled  only 


Fig.  1. — Tin'  com  leaf-aphis  (  Aphis  maidis  :  Winged  female.     Much  enlarged    original). 

by  the  problem  as  to  the  destination  of  the  winged  individual-  that 
leave  the  same  plants  in  autumn.  While  on  the  plants  they  are 
attended  by  the  little  brown  ant,  the  same  one  that  cares  for  the  root- 
aphis.  Thus  it  will  be  seen  that  we  have  but  a  fragment  of  the  life 
cycle  of  this  insect;  for,  if  it  is  a  distinct  species,  it  must  occur  else- 
where than  on  corn  long  before  July,  and  it  is  equally  clear  that  if 
distinct  it  must  migrate  in  the  fall  to  some  plant  that  will  afford  food 
for  the  young  the  following  spring,  there  to  deposit  its  eggs.  We 
judge  this  to  be  the  case,  as  it  is  known  that  with  most  species  of 
aphides  there  occurs  in  fall  a  generation  of  winged  females  that  fly 
to  the  spring  food-plant,  there  to  produce  a  generation  of  both  males 
and  females,  the  latter  laying  eggs  that  do  not  hatch  until  spring. 
From  spring   until   fall  there  are  no  males  and   no  eggs;    all  young 

[Cir.  86J 


3 


are  born  alive,  aftei  the  manner  of  mammals,  and  :ill  are  fertile 
females.  Ii  will  therefore  be  verj  clear  thai  with  no  knowledge  of 
the  males  and  with  onl)  ilii-  fragment  <»t"  tin'  life  cycle  of  the  females 
it  i-  impossible  to  saj  whether  the  leaf  aphis  i-  an  alxn  e  ground  form 
of  the  root-aphis  or  whether  it  i-  distinct  from  and  wholly  inde 
pendent  of  that  insect. 

:  hi  i>    i  \  i  'KM  mi  \  i  -. 

In  <  ).-tc »ber,  1885,  the  writer  transferred  some  volunteer  plants  of 
corn  from  the  ii«'M  of  fall  wheat,  where  thej  were  growing,  to  some 
breeding  cages.  The  plant-  were  thicklj  populated  with  winged 
females  of  the  leaf-aphis,  and  these  were  careful lj  Becured  with  the 
plant-,  both  being  subjected  to  the  same  conditions  \n  1 1  i < •  1 1  would  have 
influenced  them  had  tln\  remained  in  the  field,  except  that  the  ants  in 
attendance  were  excluded.  <  )n  Ma\  8,  188(5,  corn  was  planted  in  these 
cages  and  ipvu  therein  till  after  the  L5thof  June  when  it  was  thrown 
out  without  a  single  individual  of  either 
root  or  aerial  form  of  the  root-aphis  being 
on  or  about  t li«'  plants. 

Dr.  S.  A.  Forbes,  State  entomologist  of 
Illinois,  under  whose  direction  most  of  tin' 
investigations  of  these  insects  have  been 
carried  out,  in  summing  up  the  results  of 
a  long  series  of  careful I3  conducted  experi 
ments  of  bis  own.  comments  as  follow-: 


Wingless  female.    Much 
enlarged  (original). 


Tin'  foregoing  data  confirm   our  ignorance   more 
than  they  increase  our  knowledge,  showing,  as  they 
do,  the  Failure  "t'  all  attempts  to  find  "r  produce  a 
bisexual  generation  or  an  alternative  food  plant  of 
i  u>  Irani  how  and  where  it  normally 
sea  the  winter.     Its  willingness  to  feed  "ii  winter  wheal  and  ability  to  breed 
v  .hi  that  plant,  its  indisposition  toward  grass  or  the  foliage  of  the  apple,  and 
the  natural  frequency  of  successive  generations,  are  the  principal  other  facte  evident 
from  these  ■  ibsen  ations.*1 

Winged  females  of  the  root-aphis  occur  in  summer  on  the  leaves  of 
corn  together  with  those  of  the  leaf-aphis,  but  never  in  such  immense 
numbers.  The  two  forms  of  winged  females  seem  to  be  distinguish- 
able,  t>ut  tin-  sexes  have  never  yet  been  observed  to  interbreed 
indeed  without  males  above  ground  they  could  not  do  so;  heme  it  is 
yet  too  much  to  say  whether  there  are  two  distinct  species,  with  the 
male-  of  but  one  yet  discovered,  or  whether  these  are  two  form-  ,<\  a 
single  species,  with  as  yet  undiscovered  relationships  obscured  by 
long-continued  influences  of  ants.  A-  it  i-  with  the  root-aphis  that 
the  farmer  has  most  to  do,  that  species  will  be  chiefly  considered  here. 

'Twenty-third  Report.  -  of  Illinois,  p.  133,  1905. 


THE  CORN  ROOT-APHIS. 

Although  the  corn  root-aphis  (figs.  3,4)  was  no!  definitely  described 
until  L891,  its  presence  in  the  cornfields  <>i'  Ulinois  was  noticed  by 
Mr.  1).  1).  Walsh  in  L862,  near  Ruck  Island,  and  these  two  corn 
aphides  were  made  the  subject  of  a  paper  contributed  by  him  to 
the  Transactions  of  the  Illinois  State  Agricultural  Society."  Mr. 
Walsh,  who  was  afterwards  the  firsl  State  entomologist  of  Illinois, 
stated  thai  his  attention  was  called  to  the  "'  lice"  on  the  roots  of  corn 
in  this  field  in  the  latter  part  of  May.  L862,and  about  a  fortnight  later 
he  visited  the  field  in  person.  He  illustrates  a  section  of  corn  root 
"as  I  saw  il  with  my  own  eyes,  swarming  with  these  tiny  pests." 
Further,  he  state-  that  from  wingless  specimens,  secured  at  the  time 
of  his  visit,  lie  afterwards  reared  15  winged  female-.  From  the 
fact    thai   the  description  of  the  leaf-aphis  by  Doctor  Fitch  "agrees 


Fig.  3. — Thecorn  root-aphis     i,  male.     Much  enlarged  (original  . 

tolerably  well"  with  that  of  the  species  that  he  found  attacking  the 
roots  in  dune,  he  suspected  that  the  two  were  identical.  An  illustra- 
tion of  the  winged  female  reared  from  the  roots  does  not.  however, 
tend  to  convince  oneof  the  correctness  of  his  opinion,  as  it  best  repre- 
sents the  winged  root-aphis  and  rather  sustains  the  fact  that  the  root- 
aphides  were  present  on  the  roots  of  corn  at  that  time,  in  tin'  vicinity 
of  Rock  Island,  and  that  from  some  of  these  he  succeeded  in  rearing 
winged  adults  in  June.  While  this  is  not  in  the  least  surprising  it  is 
nevertheless  interesting  as  being  a  record  of  the  original  discovery  of 
the  root-aphis  and  of  the  discovery  and  rearing  of  the  winged  female. 
The  statement  made  that  the  root-aphis  was  attended  by  little  brown 
ants  is  still  further  evidence  of  the  validity  of  these  observations, 
however  incoi  red  Walsh's  conclusions  therefrom  may  have  been.  As 
a  matter  of  fact,  up  to  about  that  time  spring  wheat  culture  had  dorni- 


[Cir.86] 


a  Vol.  5,  pp.  491-497,  1861-64. 


nated  over  the  prairie itrj  eaal  of  the  M  »pi  River  and  north 

of  the  ohi..  River,  *o  thai  conditions  were  not  >le  for  the  rool 

aphis.      Bui   ahoul   thai   time   conditions  chan|  I    corn   culture 

became  dominant,  n  th<  •  ontinui  d  i  ultivation  of 

to  this  latter  -ruin  for  i  r  or  less  number  of 

g  this   |  '     nto  continually  inert  prominent 

Walsh's  observations  were  ma  I  the  time  of  what  was 

tabh  ill"  begin ni  of  destructivem 

~.  ft]  r  iii  in. 

For  nil  practical  purposes  the  rool  aphis  may  be  sufficiently  •  barac 
terized  as  follows:    I  lor  is  bluish  preen,  slightly  whitened  h 

mun  bloom,      l'lf  '■■•  h    i    oval,  and  on  the  anterior  pari  of  the  b 
:lll.  two  short,  slender,  rather  conspicuous  cornicles  or  tubes,  either 
standing  ereel   or    projecting    slightly  backwa 
(fig.  i).     The  \\  inged   femah  black 

head  and  brownish-black  thorax,  the  abdomen 
b  in.'-  nale  preen,  w  ith  about  three  marginal  Mack 
spots  and  numerous  small  dark  sp<  r  the 

surface.  The  antennae  are  dark,  with  paler  tinge 
at  articulations,  and  the  legs  are  mostly  black. 
The  only  form  of  male  known  is  wingless,  like 
the  female  found  on  the  roots. 

mi     ri  .1  n    v i ■  1 1 1 --    \np    i  in'    i .1 1  i  ii     BR<  >W  n     \n  i . 


Much 


Before    proceeding  further  it    is  necessary  to 
describe   a    most    important  and  astonishing 
mestic  condition  involving  the  brown  ant  (I 

1,.,  var.  •  Enierj  i  and  the  other- 

wise helpless  A  The   |  of  ants  burrow 

about   young  com    plants  in  the    field    has  frequently   attracted  the 
attention  of  farmers,  and  damages  to  the  cro  ery  frequently 

attributed  to  them.     The  species  under  consideration  is  oi f  our 

mosl  abundanl  and  widely  distributed  ants,  occurring  in  colonies 
from  fifty  to  several  hundred  in  burrows  in  the  fields.     ^  bile  it  is  ol 
itself  harmless,  it  is  in  realty  responsible  for  all  of  the 
by  the   root-aphis,  whose  lit'-'  history  and  habits  it  appears  to  h 
entirely  revolutionized,  as  will  now  be  explained. 

i  iii     HISTOB1     VST)    HABITS   OF   nil'    BOO!    \rni-. 

The  normal  life  history  of  aphides  in  general  is  as  follows:  The  win- 
ter i-  passed  in  the  egg  state  upon  or  near  the  plant  upon  which  tin- 
young  must  first  subsist  in  spring.     From  these  eggs  there  hatch  young 


aphides  thai  are  all  females  and  these  in  a  short  time  begin  to  give  birth 
to  living  young  which  are  likewise  all  females.  Thus  the  life  cycle 
goes  on,  and  though  there  is  usually  a  radical  change  of  food  plant, 
there  are  neither  c<^^s  nor  males  until  autumn,  when  there  i-  ;i  genera- 
tion consisting  of  both  males  and  females,  the  latter  depositing  eggs 
that  winter  over.  This  egg-laying  female  and  the  male  are  the  un- 
known forms  of  the  leaf-aphis. 

Now.  taking  up  the  life  history  of  the  root-aphis,  we  find  ('</<>:-  in  the 
fall,  it  is  true,  but  only  in  the  burrows  of  and  attended  by  these  ants. 
If  there  are  eggs,  egg-laying  females,  or  males  elsewhere  they  have 
yet  to  be  discovered.  The  ants  care  for  these  eggs  throughout  the 
winter,  shifting  them  about,  according  to  Forbes,  as  they  do  their  own 
young,  to  accommodate  them  to  changes  of  weather  and  moisture.  In 
spring,  the  young,  as  soon  as  they  hatch  from  these  eggs,  are  trans- 
ferred by  the  ants  to  the  roots  of  young  foxtail  grass,  smartweed,  and 
even  ragweed.  The  young  are  carried  out  to  pasture,  as  it  were,  dur- 
ing fair  weather,  but  in  bad  weather,  or  on  cold  nights,  they  are  taken 
back  to  the  burrows  of  the  ants.  The  plants  just  mentioned  are  the 
ones  that  push  up  early  in  spring  in  last  year's  corn  lands,  and  espe- 
cially in  fields  that  have  been  plowed  and  allowed  to  stand  untouched 
for  a  week  or  so.  Usually  the  farmer  plows  his  ground  in  spring  and 
pays  little  attention  to  this  early  growth  of  weeds  and  grass,  as  he  can 
generally  dispose  of  it  as  soon  as  he  begins  to  cultivate  the  corn, 
although  this  is  not  until  the  rows  of  young  plants  can  be  followed  by 
the  eye  across  an  ordinary  held.  As  >oon.  however,  as  the  corn  plants 
begin  to  show  above  ground  the  ants  not  only  transfer  the  young 
root-aphides  from  the  burrows  to  the  roots  of  corn,  but  they  will  also 
remove  them  from  the  roots  of  grass  and  weeds  and  recolonize  them 
on  the  roots  of  young  corn.  Now  these  young  aphides  are  all  females 
and  within  a  few  days  they  begin  to  give  birth  to  young,  also  all  females; 
these,  too,  are  cared  for  by  the  ants,  which  place  them  on  the  freshest 
and  most  tender  rootlets.  This  procedure  goes  on  about  the  roots  of 
corn  throughout  the  spring  and  summer.  Forbes  has  found  that 
under  the  most  favorable  artificial  conditions  there  may  be  as  many  as 
sixteen  generations  between  April  8  and  October  10,  ten  of  which  may 
coexist  at  the  same  time.  It  is  hardly  probable,  however,  that  so  many 
generations  can  exist  under  ordinary  field  conditions;  nevertheless  it 
may  be  rightly  inferred  from  this  that  the  multiplication  of  the  species 
is  enormous.  These  ants  not  only  transfer  the  root-aphides  from 
one  root  to  another  of  the  same  plant,  but  will  carry  them  from  one 
plant  to  another  a  considerable  distance  away.  In  the  spring  of  1887 
the  writer  placed  a  number  of  flowerpots  containing  young,  growing, 
uninfested  corn  plants  between  rows  of  infested  hills  of  corn  in  the 

[Clr.86 


field.  The  corn  in  the  infested  hills  wu  then  pulled  up,  exposing  the 
roots  on  which  the  aphides  were  clustered.  The  little  brown  ants  at 
once  began  i"  earn  the  aphides  t"  new  quarters,  and  the  oex!  daj  the 
latter,  some  of  them  lull  grown,  were  abundanl  on  the  roots  of  the 
corn  in  i  lif  pots,  although  there  were  none  on  them  when  the  pots  were 
I  hi  i  in  place.     Ants  were  observed  over  a  yard  awaj  from  the  plants  thai 

I  khI  I n  uprooted,  w  ii  Ii  root  aphides  in  their  mouths,  in  nil  uppearam  es 

searching  for  :i  suitable  place  in  which  to  establish  their  charges  on 
the  roots  of  corn.  Thus  it  i-  that  from  the  la\  ing  of  the  eggs  in  fall 
to  the  last  or  egg- laying  generation  of  the  following  year  this  aphis  is 
wholly  dependent  on  the  little  brown  ant  I'm-  it-  existence  in  the  culti 
vated  fields,  ami  i  In'  farmer  can  justly  charge  up  bis  losses  through  the 
attacks  of  the  root  aphisto  the  influences  of  thisant.  Bui  the  matter 
does  n"t  terminate  here,  as  will  be  seen  by  what  follows. 

WINGED    FEMALES   OF   THE    ia><  n    \riu-. 

So  long  as  the  roots  upon  which  the  root  aphides  are  colonized  afford 
an  abundance  of  nourishment  for  them,  all  will  be  wingless,  but  as 
soon  as  tin1  roots  become  tough  ami  woody  or  drj  out  there  \\  ill  be  a 
generation  of  both  winged  and  wingless  individuals,  the  former  escaping 
from  the  burrows  about  the  roots  to  il\  to  other  plants,  and  in  all 
probability  to  other  Gelds,  where  tiny  may  In-  found  on  the  leaves. 
The  ant-  usually  transfer  tin'  wingless  individuals  to  more  succulent 
root-.  I  nit  seem  to  pay  little  or  no  attention  t«>  the  winged  individuals, 
letting  these  make  their  way  out  ami  away.  But  in  May,  L887,  the 
writer  was  able  to  watch  some  of  these  winged  nomadic  individuals  in 
a  cornfield  to  which  they  had  migrated  ami  to  note  the  results  of  their 
wanderings.  A  field  of  corn  hail  been  planted  on  May  1^.  Fivedays 
later  there  came  a  heavy  rainstorm  that  flattened  the  surface  of  tin' 
ground,  which  was  soon  incrusted  by  the  action  of  wind  ami  sun. 
Four  day-  afterwards  there  were  fre-hl\    thrown  up  inouml-  of  earth 

about  some  of  the  corn  plants,  and  ants  were  busily  engaged  in  and  about 
these  ami  running  up  ami  down  over  the  young  corn.  On  examining 
these  mounds  ami  burrows  the  writer  was  surprised  to  find  winged 
root-aphides  giving  birth  to  young  on  the  roots,  attended  by  ant-. 
All  of  these  young  were  very  -mall,  at  most  hut  a  few  day-  oh  I.  Other 
winged  individuals  were  found  on  the  leaves  ami  even  on  the  Btems  of 

corn,  and  when  any  one  of  these  was  placed  where  the  ant-  could  find 
it.  it  was  promptly  captured  by  an  ant  ami  transported  to  the  rout-,  of 
the  corn.  Observation  showed  that  a-  soon  a-  the  ant-  running  about 
over  the  young  corn  plant-  found  a  w  inged  aphis  they  made  a  burrow 
about  the  base  of  a  plant,  ami  soon  domiciled  the  wanderer  on  the  root 
under  their  guardianship.  Then  when  the  aphis  began  to  give  birth 
to  young  these  were  promptly  removed  to  another  part  of  the  same 


8 

root  or  to  another  root  close  by,  and  there  watched  over  by  the  patient 
and  industrious  ants.  The  same  thing  was  observed  going  onabout 
a  young  plant  of  fox-tail  grass  in  this  same  cornfield. 

[NFLUENCES    LIKELY    TO    PRODUCE    FEMALES. 

While  the  production  of  winged  individuals  seems  to  be  brought 
about  largely  by  insufficient  foodsupply,  Forbes  is  of  the  opinion  that 
the  production  of  egg-laying  females  is  fully  as  much — it'  not  indeed 
much  more — influenced  by  the  temperature,  a  low  temperature  caus- 
ing them  to  be  produced  at  any  time,  regardless  of  generation:  and  he 
himself  has  secured  them  from  as  many  as  five  different  generations. 
In  two  cases  recorded  by  him  the  first  young  produced  developed  to 
adults  that  gave  birth  to  their  young,  whereas  the  last  developed  to 
adults  that  laid  eggs.  These  cases,  although  seeming  rather  out  of  the 
ordinary,  illustrate  the  fact  that  the  insect  may  adapt  itself  to  widely 
different  autumn  conditions:  that  is  to  say,  an  early  frost,  which  pre- 
supposes a  low  temperature,  kills  the  corn  but  does  :,ot  annihilate  the 
insect,  for  an  egg-laving  generation  is  thus  precipitated  and  the  ants 
promptly  secure  the  eggs.  This  egg-laying  generation  is  probably 
produced  in  September  or  October,  as  these  females  are  found  in  the 
burrows  of  ants  at  that  time.  Possibly  it  is  produced  earlier  to  the 
South.  Mr.  C.  N.  Ainslie,  of  this  Bureau,  one  of  the  writer's  assist- 
ants, found  the  egg  laying  females  quite  numerous  in  such  situations 
on  September  22,  at  Annapolis  Junction.  Md.  The  chief  item  of 
interest  to  the  farmer  is  the  fact  that  these  eggs  are  taken  charge  of 
by  the  ants  and  kept  through  the  winter. 

THE   ANT'S   CARE    FOR    EGGS   AM)    TOUNG    OF   THE    ROOT-APHIS. 

There  is  no  indication  that  the  ants  hunt  the  fields  for  egg-laying 
females;  on  the  contrary,  they  secure  their  supply  of  c  ggs  from  females 
kept  for  precisely  that  purpose  in  their  burrows  about  the  roots  of 
corn.  This  affords  ample  explanation  of  the  increasing  abundance  of 
root-aphides  in  fields  that  are  cultivated  to  corn  year  after  year  in 
succession,  and  it  also  points  to  a  preventive  measure.  The  object  of 
all  of  this  care  on  the  part  of  the  ants  is  to  obtain  from  the  root-aphis 
a  sweet  fluid  known  as  ""honey  dew."  Owing  to  this  peculiar  rela- 
tion, this  and  some  other  aphides  are  commonly  termed  "•ants'  cows." 
Thus  the  economic  importance  of  this  insect  and  its  association  with 
ants  is  for  practical  purposes  fully  accounted  for  and  an  explanation 
furnished  a-  to  why  farmers  are  misled  into  believing  that  it  is  the 
ants  that  actually  destroy  the  corn.  Not  only  this,  hut  a  condition  of 
affairs  is  revealed  which  shows  why  this  young  growth  of  grass  and 
weeds  that  springs  up  soon  after  the  ground  is  plowed  in  spring,  pre- 


9 

parator)  to  putting  ou(  the  young  crop,  and  which  usually  causes  the 
farmer  little  concern,  is  n  all\  of  vital  importance.     The  farnx 

ure  in  the  knowledge  thai  b<  -il.\  kill  this  growth  of  we< 

and  grass  later.     This  is  true;  l>m  he  does  m<>i  do  so  until  bis  corn 
■_:  i .  >w  ii  thai  will  permit  cultivation,  and  by  this  time  the  ants 

have  transferred  the  root  aphis  i"  the  corn.     The  aphii 
longer  depondenl   on  the   roots  of  tin  ind   weeds,  so  thai 

destruction   of  the  latter  ;ii  this  time  does  not   seriously    affi 
domestic  arrangements  of  the  ants  and  aphid 

\  \  I  t  I:  \i     ENKMIKS  OF    nil      ROOl    kPHIS. 

While  the  leaf-aphis  is  attacked  by  a  1 1< »—t  of  parasites,  the  root- 
aphis  does  in  >i  appear  to  suffer  in  the  least  from  inroads  of  either  para- 
sitic or  predaceous insect  enemies.  This  is,  perhaps,  owinj  I  to 
the  protection  offered  by  the  ants.  All  natural  checks  must  ill 
be  meteorological  influences,  and,  as  pro  iously  show  n,  these  also  are 
to  a  marked  degree  overcome  by  the  watchful  care  of  attendant  :mN. 

PR]  \  i  nii \  i    an  i>  i : i . m i : i >i  \i.   mi     - 

Preventive  measures  deal  with  the  pest  prior  to  it-  becoming  estab- 
lished "ii  the  roots  of  corn  in  the  fields;  remedial  measures,  with  di-- 
posing  of  it  afterwards. 

From  the  fact  that  in  the  midst  of  tin- corn  belt,  and  where  the 
root-aphis  is  known  t<>  prove  destructive  under  certain  conditions, 
almost  complete  immunity  is  secured  where  a  system  of  crop  rotation 
has  been  carried  oul  for  many  years,  involving  l>ut  our  coin  crop  in 
the  cycle  «>t'  rotation,  it  is  self-evident  thai  this  measure  offers  the 
greatest  protection  from  the  ravages  of  this  pest  Indeed,  it  is  only 
where  such  a  system  <>t*  crop  rotation  is  not  practicable  that  the  root- 
aphis  need  be  considered  in  farm  practice.  To  the  eastwai'd,  where 
there  is  more  general  rotation  of  crop-,  this  pesl  i\<»'<  but  little  injury. 

Unfortunately,  local  conditions,  often  extending  over  large  sections 
of  country,  will  not  permit  of  crop  rotation  being  generally  adopted, 
and  some  other  plan  more  feasible  must  be  put  into  practice.  Two 
other  methods  ma}  be  followed.  One  of  t  In -<•  is  practicable  through- 
out the  corn-growing  section  of  the  country  in  -  '  not  more 
than  normal  precipitation  limine-  the  time  intervening  between  the 
first  plowing  of  the  ground  and  the  first  cultivation  of  the  young  corn. 
The  other  i-  perhaps  best  adapted  to  the  southern  portion  of  tin- coun- 
try on  account  of  the  milder  winters. 

[Cfcr.1 


10 

STIRRING    THE   SOIL    AFTER    PLOWING    AND    BEFORE   CULTIVATING   THE   ('Hoi'. 

The  action  of  the  ants  in  colonizing  the  3*011110-  root-aphides  on  the 
roots  of  young  grass  and  weeds  that  spring  up  in  the  fields  almost 
immediately  after  plowing  in  spring  has  already  been  explained. 
Indeed,  this  is  the  only  pasturage  for  3Toung  root-aphides  that  is  avail- 
able at  that  particular  period,  and  if  this  can  be  destroyed  the  pest 
can  not  survive  until  corn  roots  are  available.  If.  then,  the  ground  is 
frequently  stirred  from  the  time  it  is  plowed  until  the  first  cultivation 
takes  place,  not  only  will  this  pasturage  for  the  pest  be  destroyed,  but 
the  homes  of  the  ants  will  be  continually  broken  up  and  a  greater  or 
less  number  of  their  own  young,  as  well  as  the  young  root-aphides, 
will  be  killed,  while  many  unhatched  eggs  of  the  pest  will  be  destroyed 
or  lost  to  the  ants.  This  measure  involves  additional  labor,  it  is  true. 
but  in  the  writer's  experience  it  has  proved  effective,  and.  beside-. 
every  up-to-date  farmer  knows  that  the  more  the  soil  is  stirred,  pul- 
verized, and  compacted  prior  to  the  first  cultivation,  the  more  thriftily 
will  his  crop  grow  when  it  is  fairly  started  and  the  more  grain  will  it 
produce.  So,  then,  the  extra  labor  involved  in  this  practice  is  not  with- 
out ample  return,  aside  from  the  fact  that  it  demoralizes  the  ants  and 
destroys  the  root-aphis.  The  only  sections  of  the  country  where  this 
is  not  strictly  true  are  some  portions  of  the  South,  where  the  planter 
must  endeavor  to  curtail  the  growth  of  stalk  in  order  to  secure  larger 
and  more  perfect  ears.  But  here,  again,  corn  is  not  the  major  crop, 
it  is  not  grown  for  several  consecutive  years  on  the  same  ground,  and 
the  root-aphis  is  not  so  excessively  abundant. 

LATE    FALL    OR    WINTER    PLOWING. 

It  is  in  the  southern  section  of  the  country  that  the  second  prevent- 
ive measure,  i.  e..  late  fall  or  winter  plowing,  can  be  best  applied. 
In  the  corn  belt  of  the  more  northern  section  of  the  Middle  West,  not 
only  is  winter  plowing,  as  a  rule,  utterly  impracticable  on  account  of 
the  more  severe  weather,  but  the  fodder,  instead  of  being  .-eeured  as 
in  the  East  and  South,  is  pastured  off  after  the  corn  has  been  husked. 
To  practice  late  fall  plowing,  or  indeed  to  fall-plow  at  all.  would  mean, 
therefore,  in  this  northern  section,  the  sacrifice  of  this  important  item 
in  farm  economy.  As  far  north  at  least  as  the  latitude  of  Washing- 
ton, however,  winter  plowing  is  frequently  entirely  practicable,  and 
there  is  little  doubt  that  it  will  prove  entirely  effective  against  the 
root-aphis. 

During  the  winter  of  1906  Mr.  John  Bowie,  of  Annapolis  Junction, 
Md..  winter-plowed  the  major  portion  of  a  60-acre  field  in  preparation 
for  corn  the  following  season.  The  plowed  portions  occupied  each  of 
two  sides  of  the  field  and  a  narrow  headland  at  one  end  ;  thus  the  un- 
plowed  area  was  left  in  the  middle  of  the  field  and  this  was  plowed  in 

[Cir.  B6] 


II 

the  spring.  <  >n  July  28  the  writer  went  over  this  field  of  corn  care 
i'iiIU  and  found  thai  over  the  spring  plowed  portion  nearly  ever)  hill 
of  corn  was  infested  l>\  the  root  aphis.  The  crop  was  an  almosl  coin 
plete  Failure.  Much  of  the  corn  bad  been  killed  oul  previous  to  the 
time  of  the  writer's  v  i-ii  and  the  remaining  pari  was  dwarfed  in  growth, 
bore  i'\\  ears,  and  Buch  :i-  it  bad  were  very  small  and  almosl  worthless. 
All  over  ili<'  winter  plowed  portion,  however,  there  was  everj  pros 
pe<  i  of  a  heavj  j  ield  of  both  stalk  and  ears,  even  to  the  narrow  head- 
land previously  mentioned.  A.n  assistant,  Mr.  Unslie,  visited  the  field 
in  late  September  and  was  able,  without  information  from  anj  person, 
to  locate,  to  a  row,  the  dividing  line  between  the  two  plowings.  This 
was  clearly  visible  on  account  of  the  difference  in  appearance  in  the 
stubble—  the  com  having  by  this  time  been  cul  and  shocked  and  also 
on  account  of  the  number,  size,  and  appearance  of  the  shocks.  There 
\\  a-  a  difference  of  fullj  two-thirds  in  favor  of  the  winter-plowed  por- 
tions of  tlii—  field.  A-  the  yield  of  the  winter-plowed  portion  was  ap- 
proximately 75  bushels  per  acre,  the  spring-plowed  would  nol  exceed 
85,  showing  a  probable  loss  of  about  50  bushels  per  acre.  At  the 
markel  price,  75  cents  per  bushel,  the  loss  would  amount  to  $37.50 
per  acre,  to  which  musl  be  added  the  loss  in  fodder.  These  figures 
show  quite  conclusively  the  amount  of  damage  this  rool  aphis  is  capable 
of  doing,  as  well  as  w  hal  can  be  accomplished  in  t  he  way  of  pn\  ention 
by  thoroughly  practical  methods. 

TIIK    DBI   OF    BAHNTABD    M  ANt'RK. 

It  seems  to  be  a  fact,  borne  out  by  field  observations,  thai  where 
ground  has  been  fertilized  with  barnyard  manure  the  root-aphis  does 

not  becom destructive.     A.s  far  hack  as  lsv'>.  on  the  experiment 

farm  of  Purdue  University,  at  Lafayette,  End.,  the  writer  made  some 
observations  which  led  to  the  conclusion  thai  proper  fertilizers  applied 
to  the  soil  are  a  general  preventive  of  damage.  This  was  clearly  pro*  ed 
by  the  appearance  of  the  crop  on  a  series  of  eighteen  plats  on  the  uni- 
versity farm.  These  plats  were  located  side  by  side  and  numbered  ] 
to  Is.  All  had  produced  corn  for  the  previous  six  crops,  those  plats 
of  even  numbers  not  ha  vine-  been  fertilized  during  thai  time.  1'lat- 
L,  7.  and  L3  had.  three  and  again  two  years  previous,  received  appli- 
cations of  gas-lime;  plats  3,  9,  and  L5  had  received  application-  of 
superphosphate-  during  the  same  year-,  while  plats  •">.  1  1.  and  17  had 
received  similar  treatment  with  barnyard  manure.  The  result,  up  to 
July,  L886,  was  that  the  corn  on  all  plat-  except  those  fertilized  by 
barnyard  manure  was  small  and  uneven  in  growth,  while  o"h  plats  5, 
LI.  and  l~  the  plants  were  fully  a  third  larger,  more  thrifty,  and  far  less 
uneven  in  height.  In  fact,  these  plats  could  he  distinguished  from 
any  of  the  others  at  a  distance  from  the  tield.  It  was  unfortunate 
[Ctl  - 


12 

• 

thai  the  carrying  on  of  the  experiments  forbade  any  examinations  of 
the  roots  in  order  to  estimate  the  relative  number  of  aphides  inhabit- 
ing each  series  of  plats. 

EXPERIMENTS   IN"   DRIVING   THE   ANTS    FROM    THE    ROOTS  OF  CORN    IX   THE    FIELD. 

During  June,  L886,  a  number  of  experiments  were  made  to  test  the 
immediate  effect  of  fertilizers,  including  salt,  upon  the  aphides,  and 
also  to  learn  it'  the  ants  could  be  induced  thereby  to  abandon  or  remove 
their  favorites  to  oilier  plants. 

The  substances  used  were  two  commercial  fertilizers  (Bunner  hone 
dust  and  hone  guano),  barnyard  manure,  and  common  salt.  A  double 
experiment  was  made  with  each.  The  first  two  substances  were  applied 
(1)  by  scattering  a  tablespoonful  on  the  surface  of  the  ground  about 
the  plant  and  sprinkling  with  water  sufficient  to  wash  it  at  once  into 
the  soil,  and  (2)  by  drawing  the  earth  away  from  the  root-,  scattering 
the  same  amount  of  fertilizer  about  the  roots,  then  replacing  the  earth, 
and  sprinkling  the  surface  less  thoroughly  than  with  the  first.  The 
barnyard  manure  was  well-rotted  and  a  quantity  sufficient  to  till  a  pint 
measure  was  used  in  the  same  way.  The  salt  was  used  in  the  same 
way  as  the  manufactured  fertilizers. 

The  result,  a  week  after,  was  that  the  '"lice"'  were  still  about  the 
roots  in  every  case,  and.  except  where  salt  was  used,  they  were  found 
in  the  midst  of  the  substances  applied.  The  salt  only  drove  them  from 
one  portion  of  the  roots  to  another.  Sand  dampened  with  kerosene 
was  then  applied  in  the  same  way.  hut  the  surface  application  had  no 
effect,  and  that  made  directly  to  the  roots  only  drove  the  aphides  from 
one  part  of  the  roots  to  another,  as  did  the  salt. 

TREATING   THE   SEED    BEFORE    PLANTING. 

During  the  last  two  years  Doctor  Forbes,  in  Illinois,  has  been  test- 
ing a  great  number  of  substances  with  a  view  to  treating  the  seed 
with  some  repellent  that  would  render  it  so  obnoxious  to  the  ants  that 
they  would  not  place  the  aphides  on  the  roots  of  the  young  plant-. 
It  has  indeed  seemed  possible  to  take  advantage  of  the  well-known 
fastidiousness  of  these  ants  and  find  something  that,  applied  to  the 
seed,  would  not  injure  its  vitality,  hut  would  give  off  an  odor  >o  dis- 
agreeable to  the  ants  that  they  would  shun  the  vicinity  of  its  applica- 
tion. The  writer  tried  something  of  this  sort  in  1887—  except  that  in 
his  experiments  substances  supposed  to  be  offensive  to  the  ants  were 
placed  in  the  soil  about  the  roots  of  the  corn — but  the  result-  were 
not  satisfactory.  In  treating  the  seed,  however,  Doctor  Forbes  seems 
to  have  had  very  encouraging  success  and  he  has  permitted  the  writer 
to  use  here  the  results  of  his  experiments,  which  are  quoted  in  brief 
as  follow-: 

[Cii  -i 


13 

found  mi  tmenl  of  seed  corn  I  icture 

itl  of  lemon  and  « I  alcohol      T"  I  gallo  »hol  add  I  pint  "i  "il  "i 

lemon,  nnd  uprinkle  and  tin  *>n- 

thia  mixture  into  • 
thai  the  Huid  II)  'ii-tiii 

share.      \  I  i  ■  ture  ia  all 

I  in. I,    w  liuli    w  ill    ! 

ii -nficld  ant,  and  tl 

long 

thei  -.  the  hill  I i 

both 

more 

ti'.  I  for 

liable  .IriiL'-i-i-,  the  '>il 
of  lemon  especially  1*  ion.     If  tl 

w  hen  shaken  up  tl 

Doctor  Forbes  h  led  by  this  means  in  reducing 

the  number  of  rool  aphides  8U  per  eenl  and  the  number  of  ant*  T'.»  per 
rent,  which  i->  certainlj  a  ver)  creditable  showing  for  tlii-  mixture. 
The  mixture  of  wood  alcohol  and  oil  <>t*  lemon  is  so  easily  made  and  the 
application  so  inexpensive  and  simple  thai  ii  is  t"  be  hoped  thai  farmers 
who  have  suffered  from  the  ravages  of  this  pesl  will  give  the  prepara 
tion  a  thorough  trial  in  their  fields.  While  local  conditions  m:i\  p 
vent  the  putting  into  practice  of  any  or  all  of  the  other  measures  of 
relief  here  adi  ised,  it  is  difficult  to  conceive  of  a  situation  thai  would 
prevent  a  farmer  from  treating  his  seed  corn  before  planting,  as 
recommended. 

Appro' 

.1  Wll   -     \\    II  S<  i\. 

s  |        | 

Washington,  I  >.  C\,  April  '.   ' 

O 


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